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Re: New LED Diffusion Lamp House for Omega D Enlargers

Originally Posted by cardiomac

In practice, I think a maximum native contrast of Grade 4 is sufficient for most purposes. For those rare occasions when a grade 5 is absolutely necessary, a #5 under-the-lens filter can be added with appropriate exposure compensation.

Re: New LED Diffusion Lamp House for Omega D Enlargers

I am very interested in all 3 size heads being proposed. I currently run a DII VC with masker. I am waiting for a 5x7 Elwood. I am picking up a 8x10 Elwood this weekend. Those 3 are operational with OE heads. My big problem is a 10X10 Fotar chassis I have that needs a head. I am very close to constructing a head, but would prefer purchasing an affordable LED head.

I have followed you, cardiomac and konakoa's experiments and eagerly await larger models. I may need multiple LED heads.

Re: New LED Diffusion Lamp House for Omega D Enlargers

A straight forward rectangular box for 5x7 that I can put on my Durst 138 with straight white light and no VC or complicated wiring is what I need. I intend to use below the lens filters. I'll take care if the lift myself as I have a special glass negative carrier. I doubt that anyone has this aftermarket carrier. I bought it from Durst USA $$$. If I can't get a light source by the end of the year I'll finish my three light unit with dichroic filters head.

Re: New LED Diffusion Lamp House for Omega D Enlargers

Blue-green light works fine if it's intense enough. That's what the Aristo V54 did. No need
for two different grids. You simply selectively use a green or blue tricolor filter below the
lens, and the appropriate wavelength passes, the other doesn't. A simple turret makes life easier (like Durst used), but quite simple in any event. Just basic split printing for VC paper. Graded paper only sees blue anyway. But if you want to get fancy, a feedback
system is nice, with a lot more potential complications if something goes wrong. All it takes
is a frazzled fluorescent ballast somewhere in the vicinity to fry solid state controls.

Re: New LED Diffusion Lamp House for Omega D Enlargers

Instead of blue / green wouldn't a white LED be brighter? Does Cree make a full spectrum white LED and in what temperature? I'm sure the new Cree LED's are going to be bright enough. Under mounted filters are a fine way to go. I have a Durst and it has the provision for turret filters. I can turn a filter in place as quickly as I can turn a knob.

Is the order, LED, driver, power supply? Do the LED's need their own individual driver or can several be on a driver.

Re: New LED Diffusion Lamp House for Omega D Enlargers

Originally Posted by Curt

Instead of blue / green wouldn't a white LED be brighter?

White LED's are just blue LED's with added phosphors to secondarily emit the longer wavelengths. The phosphors are less than 100% efficient so the white LED's generally produce less light than their underlying blue emitters.

Originally Posted by Curt

Does Cree make a full spectrum white LED and in what temperature?

Cree makes several white LED's in several color temperatures. Just be aware that all white LED's that I am aware of have a steep attenuation of output in the region between blue and green - not really an issue for BW enlargements. For color, I'm not so sure.

Originally Posted by Curt

Is the order, LED, driver, power supply? Do the LED's need their own individual driver or can several be on a driver.

Re: New LED Diffusion Lamp House for Omega D Enlargers

Blue and green are the wavelengths that VC papers respond to and you don't need any other colors to make the head work. Adding white light hurts rather than helps because it adds exposure that can't be controlled as a proportion of the total light from the head. In other words, you only want light that is the light that controls paper contrast. An ideal situation is when you have plenty of blue and green light that can be used to give the contrast you want and the exposure times you want. For me, variable contrast and constant exposure is the best feature to have for printing VC paper and its pretty straightforward (conceptually) to make it happen using only blue and green in proper mixtures.

The plus to having some white light is to make focusing by human eyesight easier. You can add a focusing aid by putting a red led in the mix if you want. Red, green, blue = white. But, I find I can focus with just the green and blue in my led head. If needed, I turn the safelight off when focusing and then the image is easy to see (in absence of any other light in the room).

Re: New LED Diffusion Lamp House for Omega D Enlargers

I am by no means a B&W VC printing expert, but I do want a cheap head for my 10X10 Fotar. I just purchased a 700 LED video light. It is 20X36 bulbs laid out in a 6x12 inch grid. Those measurements were not available from the seller. I would have preferred 8X10, duh! It has 1/2 3200K and 1/2 5600K bulbs on two dimmers. I plan to mount this in a 12X12X12 box with a DIY glass and plywood negative holder. I will then experiment with the naked setup, diffusion plastic, GG and above the negative Ilford MG filters. The box will first be matte white and then matte black depending upon testing...

Re: New LED Diffusion Lamp House for Omega D Enlargers

You may want to try two diffuser panels to prevent hot spots - this may keep the overall height of the box thinner and the light output at the negative brighter. I did this with an LED head that I made. Good luck with the project